GCSE Physics revision

Electromagnetism

The motor effect

AQA 4.7.2.1

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AQA student objectives

Learning pathway

All · Most · Some

ALL 🎯

Demonstrate the magnetic effect of a current, draw directional field patterns around a straight wire and solenoid, and explain how a solenoid increases the effect.

MOST 🎯🎯

Apply the scientific explanation of electromagnetism to a relevant example.

SOME 🎯🎯🎯

Analyse a new situation involving electromagnetism and explain the scientific reasoning.

Revision summary

Key knowledge

Read on screen, then print for Cornell-style active revision.

The Right-Hand Rule

The right-hand rule helps determine the direction of the magnetic field: curl your right hand into a fist with your thumb pointing in the direction of the current, and your fingers show the direction of the magnetic field.
If the current flows upwards, the magnetic field travels anticlockwise; reversing the current direction reverses the direction of the magnetic field.

1. The Right-Hand RuleAQA

Notes

The right-hand rule helps determine the direction of the magnetic field: curl your right hand into a fist with your thumb pointing in the direction of the current, and your fingers show the direction of the magnetic field.
If the current flows upwards, the magnetic field travels anticlockwise; reversing the current direction reverses the direction of the magnetic field.

Magnetic Fields in a Flat Circular Coil

When a wire is formed into a flat circular coil, the concentric circular magnetic fields from each side of the coil interact and stretch into ellipses.
The combined magnetic fields merge to produce a single magnetic field that runs straight through the centre of the coil.

Solenoids and Their Magnetic Fields

A solenoid is formed by winding many turns of wire closely together in a long coil, producing a strong and uniform magnetic field inside.
Outside the solenoid, the magnetic field pattern is identical to that of a bar magnet, with a north pole where field lines emerge and a south pole where they enter.

3. Solenoids and Their Magnetic FieldsAQA

Notes

A solenoid is formed by winding many turns of wire closely together in a long coil, producing a strong and uniform magnetic field inside.
Outside the solenoid, the magnetic field pattern is identical to that of a bar magnet, with a north pole where field lines emerge and a south pole where they enter.

Properties of Electromagnets

An electromagnet is only magnetic whilst current flows through the wire; switching off the power source causes the magnetic field to disappear instantly.
Reversing the direction of the current through the solenoid reverses the direction of the magnetic field, effectively swapping the north and south poles.

4. Properties of ElectromagnetsAQA

Notes

An electromagnet is only magnetic whilst current flows through the wire; switching off the power source causes the magnetic field to disappear instantly.
Reversing the direction of the current through the solenoid reverses the direction of the magnetic field, effectively swapping the north and south poles.

Increasing the Strength of an Electromagnet

Increasing the current flowing through the solenoid increases the strength of the magnetic field produced.
Increasing the number of turns in the coil whilst keeping the solenoid length the same increases the field strength.
Decreasing the length of the coil whilst keeping the number of turns the same results in more densely packed coils and a stronger magnetic field.
Adding an iron core inside the solenoid greatly increases the field strength, as iron is a soft magnetic material that becomes an induced magnet when the current is switched on and loses its magnetism when the current is switched off.

5. Increasing the Strength of an ElectromagnetAQA

Notes

Increasing the current flowing through the solenoid increases the strength of the magnetic field produced.
Increasing the number of turns in the coil whilst keeping the solenoid length the same increases the field strength.
Decreasing the length of the coil whilst keeping the number of turns the same results in more densely packed coils and a stronger magnetic field.
Adding an iron core inside the solenoid greatly increases the field strength, as iron is a soft magnetic material that becomes an induced magnet when the current is switched on and loses its magnetism when the current is switched off.